PrimeGrid’sCullen Prime Search
On 25 Jul 2009 1:11:48 UTC, PrimeGrid’s Cullen Prime Search found a world record
Cullen Mega Prime:6679881*26679881+1
The prime is PrimeGrid's largest to date. It is 2,010,852 digits long and will enter
Chris Caldwell's "The Largest Known Primes Database"(http://primes.utm.edu/primes) ranked 15th overall. It is the largest Cullen prime
found and the largest found Mega Prime using LLR.
The discovery was made by Anonymous of Japan using an Intel Xeon L5420 @2.50GHz with 6 GB RAM running Windows XP Professional. This computer took about
71 hours 58 minutes to complete the primality test.
The prime was verified on 1 Aug 2009 12:48:56 UTC, by Magnus Bergman ofSweden using an Intel Core2 Duo E6750 @ 2.66GHz with 3 GB RAM running
Windows XP Professional. This computer took about 33 hours 51 minutes tocomplete the primality test. As double checker, Magnus is awarded discoverer
credit at the Prime Pages because the primary finder failed to respond.
The credits for the discovery are as follows:

1. Magnus Bergman (Sweden), discoverer
2. PrimeGrid, et al.
3. MultiSieve, sieving program developed by Mark Rodenkirch
4. GCWsieve, sieving program developed by Geoff Reynolds
5. LLR, primality program developed by Jean Penné
Entry in "The Largest Know Primes Database" can be found here:
http://primes.utm.edu/primes/page.php?id=89536
This is only the 16th Cullen Prime found and PrimeGrid's second. Cullen numbers
were first studied by Reverend James Cullen in 1905. A Cullen prime is any prime of
the form Cn=n*2^n+1. Cn is prime for n = 1, 141, 4713, 5795, 6611, 18496, 32292,32469, 59656, 90825, 262419, 361275, 481899, 1354828, 6328548, 6679881.
Using a single PC would have taken years to find this prime. So this timely
discovery would not have been possible without the thousands of volunteers whocontributed their spare CPU cycles. A special thanks to everyone who contributed
their advice and/or computing power to the search - especially all the sievers who
work behind the scenes to make a find like this possible.
PrimeGrid’s Cullen Prime Search will continue to search for even larger primes. To
join the search please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’sCullen Prime Search
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius, which
utilizes BOINC and PRPNet to search for primes. PrimeGrid's primary goal is to bringthe excitement of prime finding to the "everyday" computer user. Simply download
the software and let your computer do the rest. Participants can choose from avariety of prime forms to search. With a little patience, you may find a large or evenrecord breaking prime.
BOINCThe Berkeley Open Infrastructure for Network Computing (BOINC) is a
software platform for distributed computing using volunteered computerresources. It allows users to participate in multiple distributed computing
projects through a single program. Currently BOINC is being developed by ateam based at the University of California, Berkeley led by David Anderson.
This platform currently supports projects from biology to math to astronomy.
For more information, please visit BOINC: http://boinc.berkeley.edu
PRPNet
PRPNet is a distributed Client/Server application, developed by MarkRodenkirch, which can be used to manage and perform primality andprobable prime tests on a list of candidate numbers. The PRPNet Client uses
LLR, Phrot, or PFGW to perform these tests.
For more information, please visit PrimeGrid’s PRPNet forum thread:
http://www.primegrid.com/forum_thread.php?id=1215
For more information about PrimeGrid and a complete list of available prime search
projects, please visit: http://www.primegrid.com